Conventionally, optical filters have been used to correct luminosity factors and to prevent declines in resolution in video cameras, digital still cameras, mobile phones with camera features, and the like.
For example, in video cameras, digital still cameras, mobile phones with camera features, and the like, solid-state image sensors for color images such as CCD and CMOS image sensors are used. Luminosity factor correction must be performed because silicon photodiodes, which are sensitive to near-infrared rays, are used in the light receiving portions of these solid-state image sensors and, and thus, in many cases, near-infrared ray cutoff filters are used.
In light adjusting devices such as diaphragm devices, diaphragm and shutter devices used in the lens optical system of video cameras, digital still cameras, mobile phones with camera features, and the like, neutral density filters and similar optical filters are used to prevent declines in resolution and the like caused by hunting or diffraction phenomena.
PET (polyethylene terephthalate), PEN (polyethylene naphthalate), and norbornene-based resins are known as raw materials for the substrate of these optical filters (Patent Literature 1). However, the glass transition temperature of these resins is low, from 70 to 180° C. and, in some cases, heat resistance is not sufficient.
Additionally, Patent Literature 2 describes an infrared ray absorption filter constituted by a polycarbonate resin having a fluorene skeleton and a coloring matter having infrared ray absorption power.